The present invention relates, in general, to mobile control systems for providing audible messages to a driver and, more specifically, to adjusting the sound level of high priority messages from navigation systems, parking aid systems, and back-up warning systems, other high priority message sources based on ambient noise level in a vehicle.
The use in motor vehicles of navigation systems and other intelligent transportation system devices, such as parking aids and back-up warning systems, are increasing. These systems may generate audible messages which need to heard by the driver. The vehicle may also include an audio entertainment system which may be employed to play the audible messages from the navigation system, for example. However, any entertainment audio (such as AM, FM, tape, CD, or cellular phone) should have a lower priority than the high priority messages from the navigation or other ITS system. Some prior art systems allow the user to set a volume level for navigation system audible messages in advance. While this preset volume may be ideal for the conditions under which it is set, ambient noise conditions, including sound output from the audio entertainment system may be much greater during actual playing of navigation messages, making the navigation messages inaudible.
Prior art systems are known for monitoring ambient noise level and boosting the audio volume in the presence of or in proportion to ambient noise. However, in an integrated system wherein an amplifier is shared between the audio and the entertainment system and the source of high priority messages signals, the low priority sound signals are also boosted, thereby impairing the audibility of the high priority message signals.
The present invention has the advantage that the sound level at which high priority message signals are heard is controlled relative to the ambient noise level including any ambient noise produced by the low priority sound signals from the entertainment audio system and being generated using a shared amplifier.
In one aspect of the invention, a method of producing audible voice messages from a priority message system in a vehicle, wherein the vehicle includes an entertainment audio system generating low priority sound signals, comprises the following steps. An ambient noise level is measured, including any sounds resulting from the low priority sound signals. A priority sound level is determined for generating high priority message signals from the priority message system in response to the measured ambient noise level. A programmable gain is adjusted for the high priority message signals in response to the priority sound level. The high priority message signals are played at the adjusted programmable gain whereby the high priority message signals are heard at a sound level which is relatively greater than the ambient noise level by a predetermined target difference.